I. Field of the Invention
The present invention relates to variable compression ratio (VCR) piston assemblies such as those disclosed in U.S. Pat. Nos. 3,156,162; 3,161,112; 3,185,137; 3,185,138; 3,303,831; 3,311,096; 3,402,662; 3,418,982; 3,450,111; 3,417,738; 3,417,739; 3,450,112; 3,527,265; 3,405,698; 3,405,697; 3,405,113; 3,407,791; 3,667,433 and 3,704,695; all owned by Applicants' assignee and more particularly to an improved construction for such piston assemblies.
II. Description of the Prior Art
In the constructions disclosed in the patents indicated above an inner piston member is connected in the usual manner to a connecting rod and an outer piston member is carried by and is movable axially relative to the inner member. Relative movement of these members varies the compression ratio of the particular cylinder in which the piston moves. Clearance spaces are provided between the top and bottom ends of the inner and outer members and these form upper and lower chambers which vary conversely in volume in relation to the relative movement of the members. An incompressible fluid such as lubrication oil is supplied to these chambers in a manner which automatically regulates movement of the members to gradually change the compression ratio until a predetermined combustion pressure has been achieved. The hydraulic system then varies the movement of the members in a manner which tends to maintain a uniform maximum combustion chamber pressure.
Copending application Ser. No. 611,863 discloses an improvement upon the assemblies disclosed and claimed in the aforementioned patents by providing a lightweight, inexpensive VCR piston constructed to minimize the effects of inertia on the discharge valve and to provide rapid response to variations in engine load.